Disclosed herein is an apparatus and method that meters fluid film in an ink jet printing system that levels or fixes liquid-ink images using ink-jet printing.
Presently, ink jet printing includes ejecting or jetting drops of liquid ink from selected nozzles of a printhead to form an image on a media substrate, such as paper. Some ink jet printers receive ink in its liquid form from containers. Other printers receive ink in a solid form.
Polydimethylsiloxane (PDMS) or other release fluid or agent can be used to promote release of the ink and media from surfaces in an ink jet printer, which can extend the usable life of the printer. Unfortunately, excessive amounts of release fluid on printer surfaces can transfer to the media and contaminate it. Applying a correct amount of release fluid to printer surfaces using a release agent management system can mitigate transfer to the media, optimize post processing performance, and lower run costs for a user.
For example, printer surfaces using release fluid can produce 2 to 100 ml of the release fluid on media. High levels of release fluid application on the media is deleterious to achieving good performance for numerous post printing operations, such as hot melt adhesive application for book binding, hot and cold laminating film application, mailing tab and label application, pressure seal application, and other printing operations. Lower release fluid levels broaden the scope of the applications that can be used on prints. On the other end of the spectrum some media demand the higher levels of release fluid on media in order to deliver acceptable printer surface life and performance. Unfortunately, release fluid application rates are not adjustable in the printer either automatically or manually.
A release agent management system that controls the amount of release fluid consists of a hard roller and a rubber roller for applying release fluid to the printer surfaces. The amount of release fluid is controlled by a metering blade riding the hard roll. This blade is critical for controlling the quality and uniformity of the release fluid. However, blades that produce acceptable films are typically difficult to manufacture, due to the edge quality requirements. Insufficient blade edge quality causes a printing system to become susceptible to producing streaks from high levels or low levels of release fluid. Dry streaks and dirt problems are exacerbated by trying to run the system at low levels of release fluid application.
For example, attempts to reduce the fluid application rate in a conventional release agent management system usually entail making the metering blade edge sharper, reducing the fluid viscosity, increasing the metering blade tip loading, and/or making a metering roller smoother. All of these management attempts can lead to increased frequency of streaks and dirt problems. To elaborate, as the ratio between blade defect size and the nominal fluid film thickness approaches 1:1 and greater, any manufacturing defect in the blade edge produces a wet streak from a hole or depression in the blade, and a dry streak from a protrusion or dirt on the edge of the blade. In addition, sensitivity to dirt and other debris increases as the fluid film thickness is decreased and increased streaking occurs when the debris lodges under a blade contact point at a roller. The streaks can impact image quality and precipitate a service call for release agent management system servicing.
Thus, there is a need for an apparatus and method that meters fluid film in an ink jet printing system.